1. Field of the Invention
The present invention relates to a process for producing bis(1,2-ethanediamine)gold chloride, as well as to a gold-plating solution containing the gold chloride.
2. Background Art
Gold plating, which has long been performed in the fields of decorations and tableware, is widely used in the electronics industry due to the excellent electrical properties of gold.
In most cases, a cyan bath containing toxic potassium cyanoaurate has generally been employed as a gold-plating solution. However, there has recently arisen increased demand for a cyan-free gold-plating solution, in view of problems resulting from use of a cyan bath, such as concerns of safety at work sites, wastewater treatment, or attack of resists of semiconductor elements.
With regard to a cyan-free gold-plating solution, J. Am. Chem. Soc., 1951, vol. 73, p4722 discloses a plating solution containing bis(1,2-ethanediamine)gold chloride as a gold compound. According to this literature, bis(1,2-ethanediamine)gold chloride is obtained through reaction of chloroauric acid and ethylenediamine monohydrate in a solvent, diethyl ether, at ambient temperature.
However, such a conventional process provides a limited yield of bis(1,2-ethanediamine)gold chloride; i.e., a yield of about 73% at most. In addition, diethyl ether used in the process is a solvent involving a problem in safety.